When forming a concrete slab or floor, the uncured concrete is placed and screeded, leveled and/or smoothed to obtain a generally flat slab of generally uniform thickness. One known method to obtain a uniform thickness of concrete of a floor or deck surface is to use small pre-fabricated metal structures or stands that have support legs, which may rest directly on the corrugated sheet metal decking or plywood form-work. A small plate may be held in position at the height equal to the desired concrete thickness above the metal deck or form work. The manual screeding process then relies on these stands as a height gauge. Some devices may even ride along the top surface of elongated stands or rails supported by the stands similar to known methods used for slabs-on-grade and elevated deck work prior to implementation of mechanized laser screeding. The stands or rails may be removed just after the screeding process completed and before the concrete begins to cure. Any remaining holes and imperfections are then filled and refinished before the concrete begins to fully harden.
Another known method for obtaining a uniform thickness of concrete on a floor or deck is to provide an ongoing series of small pre-screeded areas ahead of the actual screeding process. These small pre-screeded areas may be generally referred to or known as “wet pads”. A hand trowel may be used to strike off a roughly twelve inch (30 cm) diameter area of the pre-placed concrete at a desired height or elevation. The height or elevation of each “wet pad” may be determined by using a pre-established laser reference plane provided by a laser transmitter set-up at the site, and a hand-held laser receiver mounted to a pre-set position on a grade-stick. A series of small “wet pads” or “surface pads” are thus created at the desired thickness or elevation of concrete which serve as temporary height gages. A manual hand-screeding method will use a series of these pads as a reference.
As a typical example of the procedure, first, two wet pads are made about ten feet apart. Then, a wooden 2×4 or similar straight edge is used to strike off approximately a 12 inch (30 cm) wide by 10 foot (3 m) long surface between the two twelve inch (30 cm) diameter pads. Two of these 12 inch (30 cm) wide by 10 foot (3 m) elongated “surface-pads” are then struck off parallel to each other at a distance roughly equal to the width of the screed being used. The concrete is then struck off between these two parallel surfaces using the elongated “surface-pads” as a height reference or guides for the screed. Any excess concrete material may then be manually raked and shoveled aside by workers. Alternately, additional concrete material may be brought in and added as needed to fill any low areas. This is accomplished by at least one and often two or more workers. Any obvious low or high areas are thus detected through ongoing visual inspection by the workers and corrections to the concrete elevation or thickness are made in anticipation of the action of the screeding device. This process is subject to a number of variables which affect the quality of the surface of the concrete, including human effort and error.
Hand screeding devices are known where a vibratory device is moved over a concrete surface by hand. Examples of such devices are disclosed in U.S. Pat. No. 3,067,656 issued to Gustafsson; U.S. Pat. No. 5,244,305 issued to Lindley; and U.S. Pat. No. 5,857,803 issued to Davis et al. However, such known screeding devices typically require any grade elevation or thickness adjustments of the concrete surface to be performed by manually raking or pre-grading the uncured concrete surface to a desired grade prior to screeding the surface with the vibratory screeding device. The manual human effort and visual inspection process typically results in a concrete surface that is subject to undesired height or elevation variation. This directly affects the quality of the finished concrete surface and is measurable in terms of scientifically accepted standards known in the industry as “Floor Levelness” (F-l) and “Floor Flatness” (F-f).
Therefore, there is a need in the art for an improved screeding method and apparatus or device, which is relatively small and maneuverable, for providing a concrete slab or deck of generally uniform thickness or elevation without requiring the additional manual labor processes associated with metal stands, wet pads, pre-grading, or the like.